HIV transmission and the development of AIDS is a persistent worldwide health concern, with a disproportionate burden of infection borne by women in vulnerable populations. I have focused on developing strategies to protect against HIV-1 transmission throughout my time as a researcher, and my long-term career plan is to continue on this path until effective vaccination and prevention techniques have become widely available to those most at risk. Becoming an independent researcher will allow me to follow this goal and continue improving our knowledge about this persistent public health burden. Before human vaccine trials are undertaken, the use of non-human primate studies as precursors is generally accepted as necessary. It is thought that any efficacious vaccine strategy will need to elicit humoral immune responses against the HIV-1 envelope glycoprotein (Env). In human trials this has proven acutely problematic due to the inability of current vaccines to elicit durable antibody responses to functional forms of Env. HIV Env has a high degree of plasticity and instability, resulting in generation of non-functional Env. These aberrant forms tend to dominate immune response. I have developed approaches to overcome this biological hurdle and allow isolation of fully functional particles presenting native Env trimers. The approach presented here to use a viral sorting technique to isolate functional from nonfunctional Env containing particles and immunize rhesus macaques with native functional Env trimers displayed within their native lipid membrane of non-infectious viral particles. This approach is attractive because virus-like particles perfectly recapitulate the properties of native Env trimers. Inactivated viral vaccines are currently used to protect against a broad array of diseases. The protective effect of vaccination with these particles will be assessed in mucosal tissues 3 days after SIV challenge, before systemic spread of infection, using a novel reporter to identify any sites of infection present. Rather than waiting for viral infection to disseminate, we will assess vaccine efficacy while virus is primarily located in mucosal tissues. Innate or adaptive mechanisms restricting viral spread will be observable in the mucosa. Successful completion of this project will establish new a basis for both immunogen design and mucosal challenge that can measure vaccine efficacy 3 days after challenge. A number of techniques will be developed to enable successful completion of this efficacy study, providing training that I can leverage into an independent research career. Combining the proficiency of mentors Ronald Veazey and Thomas Hope these will give us an unprecedented look at the earliest phase of vaccine activity at the site where infection must be stopped. The training opportunities to test new protection mechanisms against HIV transmission are extremely valuable to my development as a researcher. The research program described here will couple my ability to examine the functional mechanisms of new vaccine approaches with development in the HIV prevention field.